History of For observers/2023B (No. 1)

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  • 1 (2022-12-23 (Fri) 01:03:09)

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For observers

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Contents

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Basic parameters†

Spectroscopic mode†

Specifications for TAO†

‡: 600 sec, S/N = 10 (per pixel, w/o binning), 0".35 slit, 0".7 seeing. Note that these are preliminary values.

Slit efficiency†

• The above figure is a simple calculation result when a 2D Gaussian with FWHM equal to seeing is used as the PSF of a point source.
• Since the slit length of NICE is as short as 1.5", even the widest 1.5 "x1.5" slit is difficult to completely suppress the effect of slit loss.

Sensitivity†

• The above figure shows an estimate of the sensitivity in the Y, J, H, and Ks bands when NICE is installed on the TAO telescope.
• S/N per pixel (without binning) is plotted as a function of integration time for several Vega magnitudes.
• In the calculation, a point source with flat SED, 0.5” x 1.5” slit, and seeing = 0.7” are assumed.
• These are estimates and there is no guarantee that such values will be achieved.

Imaging mode†

• Note that NICE is basically unsuitable for imaging due to its narrow field of view and large number of bad pixels.
• NICE is intended to be used for photometric observations for flux calibration of spectroscopic observations.

Specifications for TAO†

Slit viewer†

Specifications for TAO†

Efficiency†

• Due to the specifications of the NICE optical system, the incident light passes through a filter before reaching the slit viewer. Therefore, the throughput is the quantum efficiency of the CCD multiplied by the filter transmittance.

Overheads†

• The following values are estimates. They may be revised in the future after actual operations begin.

  Action	Time (min)
  Acquisition	?
  Readout	0.2
  Filter change	1
  Cross disperser change	1
  Slit change	?
  Focus adjustment	10

Important notices†

Non-simultaneous acquisition of spectra for each band†

• To obtain spectra over the entire wavelength range from 0.95 microns to 2.45 microns, it is necessary to acquire data in the I, J, H, and K modes, respectively.

Necessity of sky frame acquisition†

• Since the slit length is only 1.5", ABBA nodding cannot be performed and a pure sky frame must be obtained.

Bad pixel†

• Due to aging, the number of bad pixels has increased over the years. We have designed the echelle format to minimize the impact as much as possible, but some orders are severely affected.
• If the bad pixels have a large impact on the order of interest, the optics can be adjusted as a special process to move them to an area with fewer bad pixels.

Atmospheric dispersion†

• Since the slit viewer is an optical camera and its wavelength band is different from that of the NICE itself, the effect of atmospheric diffusion cannot be ignored in some cases.
• The effect of atmospheric diffusion becomes more significant when observing low altitude objects, which makes target acquisition more difficult and slit loss can be severe.